Conventionally, with an information processing system, a redundancy configuration of the server device is often adopted for improving availability and reliability. Thus, upon improving the processing performance of the overall system in a conventional information processing system, the scale-out method of adding/reducing physical servers in units of a plurality of server devices configuring the redundancy configuration is being broadly adopted.
Nevertheless, according to this kind of conventional scale-out method, a plurality of physical servers need to be added for redundancy even when adding the server function of only one server, and there was a problem in that costs would increase by that much.
Meanwhile, in recent years, the virtualization technology of running a plurality of virtual machines on a single physical server is become widely prevalent, and numerous inventions have been proposed for the redundancy of virtual machines. For example, PTL 1 discloses a technology of arranging, in a plurality of physical servers, a plurality of virtual machines of active systems and virtual machines of reserve systems each provided in correspondence with the foregoing virtual machines of active systems.
According to this kind of virtualization technology, even in cases of adding a group of active system virtual machines and their reserve system virtual machines (this is hereinafter referred to as the “virtual machine group”), there is an advantage in that it is not necessary to add the same number of physical servers as the number of virtual machines configuring the virtual machine group, and scale-out can be performed efficiently and inexpensively.